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Seems like my ribs are a bit too wide for the main spar. About .020-.040. Some of this I can probably take up with just a bit of extra bending in rolling over the flange, but not the entire amount in some.

Would it be acceptable to add a shim between the spar and skin? Or just rework the ribs?

I would definitely check in with Sonex. I don't believe there would be an issue with a shim. I put shims on my outboard wing ribs of my hummelbird. That was a scratch build. I had made my oak spar tooling perfect. Soon as I made it I did the center spar, but then did the outer spars a year or more later and the oak tooling changed dimension slightly. That wood is untrustworthy stuff, that is why we build metal airplanes.

Sonex1542 wrote:Seems like my ribs are a bit too wide for the main spar. About .020-.040. Some of this I can probably take up with just a bit of extra bending in rolling over the flange, but not the entire amount in some.

Would it be acceptable to add a shim between the spar and skin? Or just rework the ribs?

Too wide or do you mean too high? If the rib is only too high where the rib meets the main spar, I read somewhere, either on this forum of in the Sonex plans, about modifying the top / forward edge of the rib so that you can bend it down slightly so the skin does not end up with a very small dimple in it at each rib.

Terry

Front rib, rear rib or both? Remember the front skin is actually shimmed by the rear skin. If a shim is actually needed I agree with Bryan and doubt it will be an issue. Most Sonerai's with store bought spars need to be shimmed to avoid a dip in the skin at the spar.

Steve
Sonex 892

Primarily it was the rear rib that is slightly wider. I also thought about the possibility of the rear acting as a shim for the front, but its kinda reverse in this situation. Maybe do a deeper dive on the web for shimming the main spar. I haven't read about shimming other than the formers on the turtle deck. Moreso, I wanted to avoid the ribs entirely and found what turned out to be a 90% kit. With the wings looking 90% complete. Everything seems to be to plans, but this wasnt expected.

Thanks. Trying to wrap up the wings this year and be in the air by spring 16'

I would think that if the skins step down to the spar from the aft ribs, and the LE skin fills that step, that is perfect. I have not built my wings yet.

If I remember correctly my ribs did not exactly match the width of the spar. I scratch built #1534. I laid a sample from scrap over the spar and ribs as it will be with the skins installed to confirm the alignment. Are you scratch building or building from a kit? I may have tweeted the ribs a bit to get them just right. It has been 3 years since I made the wings. Here is a link to my builders website and Flicker. There are a lot of photos.
http://websites.expercraft.com/gripdana/
https://www.flickr.com/cameraroll

I hate auto correct. I may have "tweaked" the ribs.

The rear ribs will be higher/wider than the aft side of the main spar, since the aft wing skins attach at the forward part of the main spar. I.e. the wing skins don't necessarily contact the aft edge of the spar due to how they're folded over the spar. I'm not saying you don't need to modify your ribs, just be sure you're not trying to fix a problem that doesn't actually exist.

I am curious if anyone else has experienced this and what they did about it.